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From Shushant Arora <shushantaror...@gmail.com>
Subject Re: hbase get and mvcc
Date Tue, 17 May 2016 00:19:10 GMT
thanks!

Does puts which fall inside readpoint of ongoing scan/get are preserved in
HFile also or only in memstore and it blocks memstore flush until all
ongoing scans are completed.



On Tue, May 17, 2016 at 5:31 AM, Stack <stack@duboce.net> wrote:

> On Mon, May 16, 2016 at 4:55 PM, Shushant Arora <shushantarora09@gmail.com
> >
> wrote:
>
> > Hi
> >
> > Hbase uses MVCC for achieving consistent result for Get operations .
> > To achieve MVCC it has to maintain multiple versions of same row/cells .
> > How many max version of a row/cell does Hbase keeps at any time to
> support
> > MVCC.
> >
> > Since say multiple gets started one after the other and has not completed
> > yet and multiple puts are also occuring in between . Thus it maintains
> all
> > versions whose read point is still in use ?
> >
> >
> Yes.
>
> All ongoing Gets/Scans are registered on startup with their current
> readpoint (see HRegion; see constructor for HRegionScannerImpl). Any Put
> that falls inside the readpoint of currently ongoing Gets/Scans will be
> preserved while the Get/Scan is ongoing.
>
> St.Ack
>
>
>
> > Thanks!
> >
>

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